بسم الله الحمد لله والصلاة والسلام على رسول الله
Shaykh Muhammad Ibn Saalih al-Uthaymeen رحمه الله تعالى
Source: Fatawa Noor ‘ala-Adarb – tape no. 321
If a person sees what amazes him, does he say ‘Masha Allaah Tabarak Allaah’ or ‘Masha Allaah Tabarak Allaah la Quwwata illah billah’ – and are they all correct? If a person sees what amazes him of his wealth, what does he say? What does he say in (seeing) other than that? What is the meaning of ‘Labbayk, Innal ‘Aish, ‘Aishul Aakhirah’?
All praises are due to Allaah, Lord of the worlds and prayer and salutation upon our Prophet Muhammad, his family, his companions and those who follow them in goodness until the Day of Judgement.
If a person sees that which amazes (pleases) him, pertaining to his wealth, then he should say Masha Allaah la Quwwata illa billah, just as in the story of the companion of the two gardens, when his companion said to him: It was better for you to say, when you entered your garden: That which Allaah wills there is no power except with Allaah. This is if he sees something amazing (pleasing) with his wealth.
If he sees it in other than himself then he should say Barakallaahu Alayhi (May Allaah bless it for him) or a statement similar to it.
And if he sees something that amazes (pleases) him from the matters of the Dunya (world) he should say: Labbayk, Innal ‘Aish, ‘Aishul Aakhirah, as the Prophet صلى الله عليه وسلم used to say. So he says Labbayk – meaning an answer to you – then he said verily the (real) life is the life of the Hereafter. He makes it firm within himself at the same instance that the Dunya and whatever is within it does not remain and there is not any life in it but verily the real life is the life of the Hereafter.
Taken from: http://www.alandals.net/Node.aspx?id=16935
And Allaah knows best